1. Field of the Invention
The present invention relates to a method and apparatus for encoding and decoding a modulation code. More specifically, the invention relates to a method and apparatus for encoding and decoding a modulation code so that a data stream to be recorded onto a recording medium satisfies run length limiting k-constraints.
2. Description of the Related Art
For a modulation code, a run length limited (RLL) code is used so that a data stream to be recorded onto a recording medium satisfies specified run length limiting constraints. Encoding and decoding of the RLL code are performed according to predetermined rules. The RLL code is represented by (d, k), where “d” indicates the minimum number of consecutive zeros (0) generated between 1 and 1 in a Non Return to Zero Inverted (NRZI) signal and serves to reduce intersymbol interference, and “k” indicates the maximum number of consecutive zeros generated between 1 and 1 and serves to limit a maximum transition interval so that timing information can be extracted within a predetermined period of time. A (0, k) code referred to as a k-constraint code is used as an RLL code in commercial hard disc drives.
The RLL code is essential to system configuration but involves code rate loss according to Shannon's coding theory. As a result, the RLL code limits recording density and deteriorates system performance due to error transmission during decoding.